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Abstract:

In a transmission apparatus, a reception apparatus and a method for
performing communication using chrominance information, a transmission
apparatus includes a symbol converter to obtain a symbol from data; a
symbol modulator to generate a chrominance value based on the symbol; a
luminance controller to generate a luminance value; a color space
converter to generate an RGB value based on the luminance value and the
coordinate value; and a light emitting unit to emit light based on the
RGB value. A reception apparatus includes a visible light receiver to
receive light and to generate an electrical signal having RGB color
information of the light; a color space converter to generate a luminance
value and a chrominance value based on the RGB color information; a
symbol demodulator to obtain a symbol based on the chrominance value; and
a data converter to convert the symbol to data.

Claims:

1. A transmission apparatus, comprising: a symbol converter to obtain a
symbol from data; a symbol modulator to generate a chrominance value
based on the symbol; a luminance controller to generate a luminance
value; a color space converter to generate an RGB value based on the
luminance value and the chrominance value; and a light emitting unit to
emit light based on the RGB value.

2. The transmission apparatus of claim 1, wherein the symbol modulator
maps the symbol at a signal point of a chrominance plane, and generates a
coordinate value of the signal point as the chrominance value.

3. The transmission apparatus of claim 2, wherein the chrominance plane
is a two-dimensional plane having chrominance information, and the
chrominance information comprises the coordinate value comprised of two
types of chrominance values.

4. The transmission apparatus of claim 2, wherein the chrominance plane
is a U-V plane of a YUV color space or an I-Q plane of a YIQ color space.

5. The transmission apparatus of claim 4, wherein the I-Q plane comprises
multiple signal points having an I value and a Q value as the coordinate
value, differences among the Q values of the multiple signal points are
smaller than differences among the I values of the multiple signal
points, and the symbol is mapped at a signal point among the multiple
signal points.

6. The transmission apparatus of claim 2, wherein the symbol modulator
comprises a constellation having coordinate values of multiple signal
points in the chrominance plane, the symbol is mapped at a corresponding
signal point among the multiple signal points.

7. The transmission apparatus of claim 6, wherein the constellation is
determined in an area of the chrominance plane, and differences among
chrominance values of signal points in the area are less sensitive to a
human eye than differences among chrominance values of signal points in
at least one other area of the chrominance plane.

8. The transmission apparatus of claim 2, wherein the symbol modulator
comprises a constellation having coordinate values of multiple signal
points of the chrominance plane, each of the multiple signal points
corresponds to a symbol, and a number of the multiple signal points is a
power of two.

9. The transmission apparatus of claim 1, further comprising: a
digital-to-analog (D/A) converter to convert the RGB value to an analog
signal having RGB color information corresponding to the RGB value,
wherein the light emitting unit emits the light based on the analog
signal.

10. A reception apparatus, comprising: a visible light receiver to
receive light and to generate an electrical signal having RGB color
information of the light; a color space converter to generate a luminance
value and a chrominance value based on the RGB color information; a
symbol demodulator to obtain a symbol based on the chrominance value; and
a data converter to convert the symbol to data.

11. The reception apparatus of claim 10, wherein the symbol demodulator
demaps the chrominance value at a signal point of a chrominance plane
among determined signal points, and obtains the symbol corresponding to
the signal point.

12. The reception apparatus of claim 11, wherein the chrominance plane is
a two-dimensional plane having chrominance information, and the
chrominance information comprises a coordinate value comprised of two
types of chrominance values.

13. The reception apparatus of claim 11, wherein the chrominance plane is
a U-V plane of a YUV color space or an I-Q plane of a YIQ color space.

14. The reception apparatus of claim 11, further comprising: an equalizer
to control the electrical signal or the digital signal based on the
luminance value.

15. The reception apparatus of claim 14, wherein the equalizer controls
signal strength of the electrical signal based on the luminance value to
regulate the luminance value.

16. The reception apparatus of claim 14, wherein the equalizer controls
the RGB value of the digital signal based on the luminance value to
regulate the luminance value.

17. The reception apparatus of claim 14, wherein the equalizer controls
the electrical signal or the digital signal with reference to a reference
luminance value generated by a luminance controller of a transmission
apparatus.

18. The reception apparatus of claim 10, further comprising: an
analog-to-digital (A/D) converter to convert the electrical signal to a
digital signal having an RGB value corresponding to the RGB color
information, wherein the color space converter generates the luminance
value and the chrominance value based on the RGB value.

19. A method for transmitting data using chrominance information,
comprising: converting data to a symbol; generating chrominance
information based on a signal point corresponding to the symbol;
generating a luminance value; generating red, green, and blue (RGB)
values based on the luminance value and the chrominance information;
converting the RGB values to an analog signal; and emitting visible light
based on the analog signal.

20. The method of claim 19, wherein the generating of the chrominance
information comprises: mapping the symbol at the signal point based on a
constellation; and generating a coordinate value of the signal point as
the chrominance information, wherein the constellation comprises mapping
information between the symbol and the signal point, and the signal point
is a coordinate in a chrominance plane.

21. A method for receiving data using chrominance information,
comprising: receiving visible light; generating an electrical signal
having red, green, blue (RGB) color information based on the visible
light; converting the electrical signal to a digital signal having RGB
values corresponding to the RGB color information; generating a luminance
value and a chrominance value based on the RGB values; obtaining a symbol
based on the chrominance value; and converting the symbol to data.

22. The method of claim 21, wherein the obtaining of the symbol
comprises: obtaining a coordinate value corresponding to the chrominance
value from a chrominance plane; obtaining information of signal points
based on a constellation; demapping the chrominance value at a nearest
signal point among the signal points based on the coordinate value; and
obtaining a symbol corresponding to the nearest signal point, wherein the
constellation comprises demapping information between the symbol and the
nearest signal point.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from and the benefit under 35
U.S.C. §119(a) of Korean Patent Application No. 10-2010-0116002,
filed on Nov. 22, 2010, which is incorporated by reference for all
purposes as if fully set forth herein.

BACKGROUND

[0002] 1. Field

[0003] The present disclosure relates to an apparatus and a method for
performing communication using chrominance information, and more
particularly, to an apparatus and a method for transmitting and receiving
data using chrominance information in a visible light communication
system.

[0004] 2. Discussion of the Background

[0005] Visible light communication technology is a wireless communication
technology that transmits information using visible light. Visible light
waves have wavelengths in the visible light wavelength band that may be
recognized by a human eye. The visible light communication technology is
distinguished from conventional wired optical communication technologies
and an infrared wireless communication in an aspect of using visible
light, and from a wired optical communication technology in an aspect of
a wireless communication.

[0006] The visible light communication technology may be utilized without
a regulation or permission for using frequency bands in comparison with
widespread radio frequency (RF) wireless communication. Also, the visible
light communication technology provides better physical security, and a
communication link of visible light communication may be visually
recognized by a user. In addition, the visible light communication
technology has a characteristic as a convergence technology that may
fulfill both an original purpose of providing lighting as a light source,
and a communication process.

[0007] Meanwhile, some lighting devices using a Light Emitting Diode (LED)
have a driving circuit, i.e., a LED driver to receive a control signal
and power supply required for controlling brightness and colors of the
LED. If a communication signal for visible light wireless communication
is received by an LED device, strength-modulated light is emitted from
the LED device. If an LED lighting device is used for visible light
wireless communication, the LED lighting device provides light and
performs a transmitter process of wireless communication.

[0008] There are several considerations to maintain lighting performance
of an LED lighting device when the LED lighting device is used as a
visible light communication device. For example, an anti-flicker
capability, brightness control of the lighting of the LED lighting
device, availability of a maximum brightness of the lighting, protection
of an LED light source, and prevention of color variation may be
considered. A flicker is a change in brightness of a light source that
may be recognized by a human eye, and a flicker phenomenon may appear in
a LED lighting device that emits strength-modulated light for visible
light communication.

[0009] However, the flicker phenomenon may be harmful to a human eye and
may cause psychological harm, thus the anti-flicker capability is desired
for a lighting device. The other considerations besides the anti-flicker
capability are mostly associated with brightness control of the lighting.

SUMMARY

[0010] Exemplary embodiments of the present invention provide an apparatus
and a method for transmitting and receiving data using chrominance
information in a visible light communication system.

[0011] Additional features of the invention will be set forth in the
description which follows, and in part will be apparent from the
description, or may be learned by practice of the invention.

[0012] An exemplary embodiment of the present invention discloses a
transmission apparatus including a symbol converter to obtain a symbol
from data; a symbol modulator to generate a chrominance value based on
the symbol; a luminance controller to generate a luminance value; a color
space converter to generate an RGB value based on the luminance value and
the chrominance value; and a light emitting unit to emit light based on
the RGB value.

[0013] An exemplary embodiment of the present invention discloses a
reception apparatus including a visible light receiver to receive light
and to generate an electrical signal having RGB color information of the
light; a color space converter to generate a luminance value and a
chrominance value based on the RGB color information; a symbol
demodulator to obtain a symbol based on the chrominance value; and a data
converter to convert the symbol to data.

[0014] An exemplary embodiment of the present invention discloses a method
for transmitting data using chrominance information including converting
data to a symbol;

[0015] generating chrominance information based on a signal point
corresponding to the symbol; generating a luminance value; generating
red, green, and blue (RGB) values based on the luminance value and the
chrominance information; converting the RGB values to an analog signal;
and emitting visible light based on the analog signal.

[0016] An exemplary embodiment of the present invention discloses a method
for receiving data using chrominance information including receiving
visible light; generating an electrical signal having red, green, blue
(RGB) color information based on the visible light; converting the
electrical signal to a digital signal having RGB values corresponding to
the RGB color information; generating a luminance value and a chrominance
value based on the RGB values; obtaining a symbol based on the
chrominance value; and converting the symbol to data.

[0017] It is to be understood that both the foregoing general description
and the following detailed description are exemplary and explanatory and
are intended to provide further explanation of the invention as claimed.
Other features and aspects will be apparent from the following detailed
description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a
part of this specification, illustrate embodiments of the invention, and
together with the description serve to explain the principles of the
invention.

[0019] FIG. 1 is a diagram illustrating a transmission apparatus to
transmit data using chrominance information in a visible light
communication system according to an exemplary embodiment of the present
invention.

[0020] FIG. 2 is a diagram illustrating a reception apparatus to receive
data using chrominance information in a visible light communication
system according to an exemplary embodiment of the present invention.

[0021] FIG. 3 is a flowchart illustrating a method for transmitting data
using chrominance information according to an exemplary embodiment of the
present invention.

[0022] FIG. 4 is a flowchart illustrating a method for receiving data
using chrominance information according to an exemplary embodiment of the
present invention.

[0023] FIG. 5 is a diagram illustrating a U-V plane in a YUV color space
according to an exemplary embodiment of the present invention.

[0024] FIG. 6A is a diagram illustrating a constellation having four
signal points on a U-V plane according to an exemplary embodiment of the
present invention.

[0025] FIG. 6B is a diagram illustrating a constellation having four
signal points on a I-Q plane according to an exemplary embodiment of the
present invention.

[0026] FIG. 7 is a diagram illustrating a constellation having eight
signal points on a U-V plane according to an exemplary embodiment of the
present invention.

[0027] FIG. 8 is a diagram illustrating a constellation having sixteen
signal points on a U-V plane according to an exemplary embodiment of the
present invention.

[0028] FIGS. 9A through 9E are diagrams illustrating examples of applying
constellation 4 CDSK (Correlation Delay Shift Keying) to a partial area
of a U-V plane according to an exemplary embodiment of the present
invention.

[0029] FIG. 10 is a diagram illustrating a method for determining a symbol
corresponding to chrominance information of received visible light
according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0030] Exemplary embodiments now will be described more fully hereinafter
with reference to the accompanying drawings, in which exemplary
embodiments are shown. The present disclosure may, however, be embodied
in many different forms and should not be construed as limited to the
exemplary embodiments set forth herein. Rather, these exemplary
embodiments are provided so that the present disclosure is thorough, and
will fully convey the scope of the invention to those skilled in the art.

[0031] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the
present disclosure. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. Furthermore, the use of the terms a,
an, etc. does not denote a limitation of quantity, but rather denotes the
presence of at least one of the referenced item. The use of the terms
"first", "second", and the like does not imply any particular order, but
they are included to identify individual elements. Moreover, the use of
the terms first, second, etc. does not denote any order or importance,
but rather the terms first, second, etc. are used to distinguish one
element from another. It will be further understood that the terms
"comprises" and/or "comprising", or "includes" and/or "including" when
used in this specification, specify the presence of stated features,
regions, integers, steps, operations, elements, and/or components, but do
not preclude the presence or addition of one or more other features,
regions, integers, steps, operations, elements, components, and/or groups
thereof.

[0032] Exemplary embodiments of the present invention provide a
transmission apparatus, a reception apparatus, and a method for
performing transmission of data using a chrominance value in a visible
light communication system. Human vision has less spatial sensitivity to
chrominance differences than luminance differences. Luminance may be
referred to as `luma` and represents the brightness in an image or
achromatic portion of an image.

[0033] YUV is a color space that may be used as part of a color image
pipeline. YUV is a standard representing a color like RGB. The RGB color
model is an additive color model in which red, green, and blue light is
added to reproduce various colors. The RGB color space defines signal
information with respect to primary colors whereas the YUV is a color
space defining signal information with respect to brightness and
chrominance. More specifically, Y refers to luminance, U refers to Blue
color-Y (B-Y), and V refers to a Red color-Y (R-Y). This color
information such as U and V is called chrominance. Chrominance may be
represented as two color-difference components, U and V, however it is
not limited as such. A human eye is more sensitive to the change of Y
component than to the change of U and V components.

[0034] In visible light spectrum distribution, green color (G) has high
luminance, and a color component of the G is broadly distributed in the
spectrum. Thus, a human eye may be more sensitive to the change of the G
component. Accordingly, exemplary embodiments of the present invention
provide a U-V plane that may minimize sensitivity for a human eye while
locations of symbols are changing in the U-V plane.

[0035] FIG. 1 is a diagram illustrating a transmission apparatus to
transmit data using chrominance information in a visible light
communication system according to an exemplary embodiment of the present
invention.

[0036] As shown in FIG. 1, the transmission apparatus 100 may include a
symbol converter 110, a symbol modulator 120, a luminance controller 130,
a color space converter 140, a digital-to-analog (D/A) converter 150, and
a light emitting unit 160.

[0037] The symbol converter 110 may convert a bit stream of data to a
symbol used for mapping the bit stream of the data on a U-V plane. The
U-V plane may be represented as illustrated in FIG. 5.

[0038] FIG. 5 is a diagram illustrating a U-V plane in a YUV color space
according to an exemplary embodiment of the present invention.

[0039] The YUV is a color space represented by luminance information and
chrominance information, and the U-V plane is a two-dimensional plane
defined by two chrominance values, a U value and a V value. Referring to
FIG. 5, the U value is indicated as an x-coordinate value, and the V
value is indicated as a y-coordinate value. When the luminance value, Y,
is 0.5, an example of U-V plane is depicted in FIG. 5. Large portions of
quadrant I of the U-V plane display purple. Large portions of quadrant
II, the quadrant III, and the quadrant IV of the U-V plane display red,
green, and blue, respectively. The chrominance information may include a
coordinate of a chrominance plane, or a chrominance value such as the U
value, and the V value.

[0040] The symbol modulator 120 may perform mapping of the symbol
converted by the symbol converter 110 on a signal point of the U-V plane
using a determined constellation of the symbol, and may output a U-V
coordinate value of the signal point corresponding to the symbol. The
determined constellations in the transmission apparatus 100 and a
reception apparatus 200 may be inverses of each other. Thus, a symbol may
be mapped into a coordinate value by the transmission apparatus 100, the
coordinate value may be demapped into the symbol by the reception
apparatus 200. A constellation may refer to a fixed group of signal
points in communication systems. The signal points may include matching
symbol information and signal points information. However, throughout the
specification, a constellation may be a signal point in a chrominance
plane, a coordinate value of the signal point in a chrominance plane, or
chrominance information of each symbol in a chrominance plane such as U,
V, I, and Q values.

[0041] The symbol modulator 120 may modulate the symbol based on a U-V
plane of a YUV, however, the modulation of the symbol may not be limited
to the U-V plane of the YUV. The modulation of the symbol may be
performed using any color space represented with luminance and
chrominance information. The modulation of the symbol may also be
performed using chrominance information of YIQ. The YIQ is the color
space used by the NTSC color TV system. I stands for in-phase, and Q
stands for quadrature, referring to the components used in quadrature
modulation. I and Q represent chrominance information. An example of an
I-Q plane of the YIQ color space is illustrated in FIG. 6B.

[0042] That is, the U-V plane may be one type of color space on which
chrominance information is represented as a two-dimensional plane among
color space standards represented by luminance information and
chrominance information. The YIQ color space may be a plane represented
with red and blue colors.

[0043] The determined constellation of the symbol showing a coordinate of
a signal point correspond to the symbol may be represented as illustrated
in FIG. 6, FIG. 7, and FIG. 8 according to the size of the symbol.

[0044] FIG. 6A is a diagram illustrating a constellation having four
signal points on a U-V plane according to an exemplary embodiment of the
present invention.

[0045] Referring to FIG. 6A, a constellation of a 2-bit symbol may be
represented by four signal points corresponding to four different
symbols, respectively. As shown in FIG. 6A, the constellation of the
2-bit symbols may be represented by four coordinates including a U value
and a V value on a two-dimensional U-V plane. The four coordinates (u1,
v1), (u2, v1), (u1, v2), and (u2, v2), the four signal points on each
corner of the U-V plane, may be represented as symbols (00), (10), (01),
and (11), respectively. The constellation of the 2-bit symbol may be used
to obtain a U value and a V value with respect to the symbol by the
symbol modulator 120.

[0046] FIG. 6B is a diagram illustrating a constellation having four
signal points on a I-Q plane according to an exemplary embodiment of the
present invention.

[0047] Referring to FIG. 6B, a constellation of a 2-bit symbol may be
represented by four signal points corresponding to four different
symbols, respectively. As shown in FIG. 6B, the constellation of the
2-bit symbols may be represented by four coordinates including an I value
and a Q value on a two-dimensional I-Q plane. The four coordinates (0,
3q1), (0, q1), (0, -q1), and (0, -3q1), the four signal points or the
constellation of the I-Q plane, may be represented as symbols (00), (10),
(01), and (11), respectively. The constellation of the 2-bit symbol may
be used to obtain an I value and a Q value with respect to the symbol by
the symbol modulator 120.

[0048] In the YIQ color space, a human eye is more sensitive to changes in
the red-blue range ("I range") than in the purple-green range ("Q
range"). Thus, if signal points are arranged vertically, for example, the
signal points have the same I values and different Q values as shown in
FIG. 6B, a human eye may not notice the difference. In this instance,
better lighting may be provided during visible light communication. If
signal points are arranged horizontally, for example, the signal points
have the same Q values and different I values, the visible light
communication may be more noise-resistant because blue color and red
color are less associated with each other in visible light spectrum.

[0049] In the same way, if signal points are arranged along the red-blue
range in the U-V plane, visible light communication may be more
noise-resistant because blue color and red color are less associated with
each other in visible light spectrum. For example, signal points of the
U-V plane in FIG. 6A may be arranged along the line of which the slope is
-1 to be more noise-resistant in comparison with signal points
illustrated in FIGS. 9A through 9E.

[0050] The constellation may be changed according to communication
environment. If visible communication error occurs frequently due to
noise, the constellations of a transmission apparatus and a reception
apparatus may be changed into relatively more noise-resistant
constellation. If visible communication error does not occur frequently,
the constellations of a transmission apparatus and a reception apparatus
may be changed such that the chrominance differences among the signal
points are less sensitive to a human eye.

[0051] FIG. 7 is a diagram illustrating a constellation having eight
signal points on a U-V plane according to an exemplary embodiment of the
present invention.

[0052] Referring to FIG. 7, a constellation of a 3-bit symbol may be
represented by eight signal points corresponding to eight different
symbols, respectively.

[0053] FIG. 8 is a diagram illustrating a constellation having sixteen
signal points on a U-V plane according to an exemplary embodiment of the
present invention.

[0054] Referring to FIG. 8, a constellation of a 4-bit symbol may be
represented by sixteen signal points corresponding to sixteen different
symbols, respectively.

[0055] The symbol modulator 120 may generate the constellation of the
symbol using only a partial area of the U-V plane for a user who is
sensitive to chrominance change. The partial area of the U-V plane is an
area where the user may not recognize chrominance differences with an eye
of the user. The examples of the partial area of the U-V plane are
illustrated in FIGS. 9A through 9E.

[0056] FIGS. 9A through 9E are diagrams illustrating examples of applying
constellation 4 CDSK (Correlation Delay Shift Keying) to a partial area
of a U-V plane according to an exemplary embodiment of the present
invention.

[0057] FIGS. 9A through 9E are examples of generated constellations of a
symbol in an area where a user may not recognize chrominance differences
with an eye of the user.

[0058] The luminance controller 130 may generate a luminance value of Y.
The luminance value generated by the luminance controller 130 may be used
to maintain a constant luminance value for a color signal.

[0059] The color space converter 140 may generate red, green, and blue
(RGB) values using the Y value generated by the luminance controller 130
and the U-V coordinate values including a U value and a V value generated
by the symbol modulator 120. In an example, the YUV-to-RGB conversion may
be performed according to the following equation, Equation 1:

R=Y+1.402V

G=Y-0.344U-0.714V

B=Y+1.772V Equation 1

[0060] With reference to FIG. 1, the D/A converter 150 may convert each of
the RGB values generated in the color space converter 140 to an analog
signal. The D/A converter 150 may include three digital-to-analog
converters for R, G, and B values which represent for red, green and blue
color, respectively. Each of the RGB values may be converted to a
separate analog signal or an RGB value may be converted to an analog
signal having RGB color information. The RGB value may mean a value
including a red (R) value, a green (G) value and a blue (B) value or may
mean each of RGB values, that is, R value, G value, and B value.

[0061] The light emitting unit 160 may emit visible light for each color
based on the analog signal transmitted from the D/A converter 150.

[0062] FIG. 2 is a diagram illustrating a reception apparatus to receive
data using chrominance information in a visible light communication
system according to an exemplary embodiment of the present invention.

[0063] As shown in FIG. 2, the reception apparatus 200 may include a
visible light receiver 210, an analog-to-digital (A/D) converter 220, a
color space converter 230, an equalizer 240, a symbol demodulator 250,
and a data converter 260.

[0064] The visible light receiver 210 may receive a visible light signal
of RGB and convert the visible light signal to an electrical signal for
each of RGB colors. The visible light receiver 210 may include a photo
diode, an image sensor, and the like. The visible light receiver 210 may
include three sensors to sense red, green, and blue colors, respectively.

[0065] The A/D converter 220 may convert the electrical signal converted
in the visible receiver 210 to a digital signal for each of RGB colors.
The A/D converter 220 may include three analog-to-digital converters for
R, G, and B values which represent for red, green and blue.

[0066] The color space converter 230 may convert the digital signal of RGB
colors converted by the A/D converter 220 to a YUV value. The digital
signal of RGB colors may include an RGB value. The RGB-to-YUV conversion
may be performed according to the following equation, Equation 2:

Y=0.299R+0.587G+0.114B

U=0.564(B-Y)

V=0.713(R-Y) Equation 2

[0067] The equalizer 240 may control the digital signal outputted from the
A/D with the Y value outputted from the color space converter 230.
Further, the equalizer 240 may control the electrical signal for each of
RGB colors outputted from the visible light receiver 210 with the Y value
outputted from the color space converter 230. For example, if the Y value
is higher than a reference value, the equalizer 240 may reduce a value of
the RGB signal outputted from the A/D converter 220. If the Y value is
lower than the reference value, the equalizer 240 may increase a value of
the RGB signal outputted from the A/D converter 220. For example, the RGB
values may be scaled up or down to regulate the Y value. Then, the U
value and the V value may be controlled according to the equation 2. The
reference value for Y may be determined with reference to the Y value of
the luminance controller 130 of the transmission apparatus 100.

[0068] The symbol demodulator 250 may perform demapping of the obtained
chrominance values, U and V values, at the nearest signal point based on
the U value and the V value converted by the color space converter 230,
and output a symbol corresponding to the demapped signal point.
Hereinafter, an example of demapping in the symbol demodulator 250 will
be described with reference to FIG. 10.

[0069] FIG. 10 is a diagram illustrating a method for determining a symbol
corresponding to chrominance information of received visible light
according to an exemplary embodiment of the present invention.

[0070] Information received by the visible light receiver 210 may not
correspond to information transmitted from the transmission apparatus 100
due to noise. For example, some signal points on a U-V plane of the
transmission apparatus 100 are defined as (U1, V1) and (U2, V2), and
acquired U and V values of a signal, transmitted from the transmission
apparatus 100, on a U-V plane of the reception apparatus 200 may be
defined as (U', V').

[0071] The symbol demodulator 250 may determine the nearest signal point
from the obtained U and V values (U', V') among signal points (U1, V1)
and (U2, V2), and may determine the signal point (U1, V1) which is closer
to (U', V') than the signal point (U2, V2) as a corresponding signal
point. The transmission apparatus 100 and the reception apparatus 200 may
have determined signal points, such as (U1, V1) and (U2, V2), by sharing
symbol mapping information.

[0072] The data converter 260 may convert the symbol outputted from the
symbol converter 250 into corresponding data.

[0073] Hereinafter, a method for transmitting and receiving data using
chrominance information in a visible light communication system will be
described with reference to FIG. 3 and FIG. 4.

[0074] FIG. 3 is a flowchart illustrating a method for transmitting data
using chrominance information according to an exemplary embodiment of the
present invention.

[0075] Referring to FIG. 3, a transmission apparatus may receive input
data in operation 310. Then, the transmission apparatus may convert the
input data to a symbol to map the input data on a U-V plane in operation
312.

[0076] In operation 314, the transmission apparatus may map the symbol at
a signal point of the U-V plane and modulate the symbol by generating a
coordinate value of the U-V plane having a U value and a V value
corresponding to the signal point of the symbol.

[0077] In operation 316, the transmission apparatus may generate a
luminance value Y, and may convert the Y value, the U value, and the V
value to a digital RGB signal. The value of the luminance value Y may be
determined to maintain a constant luminance value of output visible
light.

[0078] In operation 318, the transmission apparatus may convert the
digital RGB signal to analog signal. In operation 320, the transmission
apparatus may emit visible light for each RGB color based on the analog
signal for each of the RGB colors.

[0079] FIG. 4 is a flowchart illustrating a method for receiving data
using chrominance information according to an exemplary embodiment of the
present invention.

[0080] Referring to FIG. 4, a reception apparatus may receive visible
light of RGB and convert the visible light to an electrical signal for
each of the RGB colors, in operation 410. The visible light of RGB may be
sensed by three image sensors for sensing each of the RGB colors.

[0081] In operation 412, the reception apparatus may convert the
electrical signal ("analog signal") to a digital signal for each RGB
colors. In operation 414, the reception apparatus may convert the digital
signal of RGB to YUV values.

[0082] In operation 416, the reception apparatus may demap chrominance
value at the nearest signal point based on the U value and the V value,
and demodulate the demapped signal point to a symbol corresponding to the
demapped signal point. In operation 418, the reception apparatus may
convert the symbol to corresponding data. The reception apparatus may
output the data in operation 420.

[0083] The exemplary embodiments according to aspects of the present
invention may be recorded in non-transitory computer-readable media
including program instructions to implement various operations embodied
by a computer. The media may also include, alone or in combination with
the program instructions, data files, data structures, and the like. The
media and program instructions may be those specially designed and
constructed for the purposes of the present invention, or they may be of
the kind well-known and available to those having skill in the computer
software arts.

[0084] In an apparatus and a method for performing communication using
chrominance information, each symbol of data may be represented as a
constellation in a chrominance plane. Multiple symbols may be
distinguished from each other by chrominance information of red color and
chrominance information of blue color while maintaining a constant or
similar luminance value. The data modulated by using chrominance
information of blue color and chrominance information of red color may be
noise-resistant, because blue color and red color is less associated with
each other in the visible light spectrum. In addition, a flicker
phenomenon may be reduced by reducing changes of luminance value of the
visible light while transmitting data using the constellation in the
chrominance plane.

[0085] It will be apparent to those skilled in the art that various
modifications and variation can be made in the present invention without
departing from the spirit or scope of the invention. Thus, it is intended
that the present invention cover the modifications and variations of this
invention provided they come within the scope of the appended claims and
their equivalents.

Patent applications by Yeon Moon Lee, Goyang-Si KR

Patent applications by PANTECH CO., LTD.

Patent applications in class OPTICAL COMMUNICATION OVER FREEE SPACE

Patent applications in all subclasses OPTICAL COMMUNICATION OVER FREEE SPACE